Those skilled in the art are cognizant of a variety of shutter designs, including shutters having a central opening closed by movable slats. Examples include Wharry, U.S. Pat. No. 73,213; Ingram, U.S. Pat. No. 176,789; Wendelken, U.S. Pat. No. 1,238,703; Dubour, et al., U.S. Pat. No. 2,311,300; Huff, U.S. Pat. No. 2,317,994; Brown, U.S. Pat. No. 2,359,289; and Grabove, U.S. Pat. No. 2,877,841.
Commonly, such shutters employ one of two basic types of mechanisms to coordinate the movement of the slats. In the first, a vertical bar is attached in common to all of the slats. The slats then rotate in a coordinated manner about their longitudinal axes on pins that are driven into the surrounding body of the shutter. Ingram illustrates an early example of such a structure. Other shutters include slats the ends of which are mounted in mechanisms that are moved simultaneously by means of a mechanical linkage operating at the sides of the shutter. Wharry, Wendelken, Dubour, et al., Huff, and Grabove, all present examples of such structures.
In all of the examples referred to above, the slats are attached to the surrounding body of the shutter at the ends of the slats by means of a mechanism that is subject to being broken or bent if the slats sustain a blow or are otherwise stressed. Likewise, moving parts located at the ends of the slats are exposed to dust and grime introduced with the air passing through the shutter. Consequently, the shutter's working parts are especially subject to being jammed, stuck, or simply impeded by distortion or buildup of foreign matter.